Last year, a monster magnet set out from Brookhaven National Lab on an epic trek by land and sea to Fermilab, where it will serve as the heart of a search for evidence of new subatomic particles. Last month, researchers came to SLAC to test the eyes and nerves of the same experiment: a cutting-edge design for a new detector.

Step on a scale and you’ll get a quick measure of your weight. Weighing galaxy clusters, groups of hundreds or thousands of galaxies bound together by gravity, isn’t so easy. But scientists have many ways to do it.